Operator&#39;s circuits



H. T. WHITE.

OPERATOR'S CIRCUITS- APPLICATION man same. 1917.

Patented Apr. 4, 1922.

UNITED STATES PATENT OFFICE.

HAROLD '1. WHITE, OF KANSAS CITY, KANSAS, ASSIGNOR TO KELLOGG SWITGHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

OPERATORS CIRCUITS.

Specification of Letters Patent.

Patented Apr. 4, 1922.

Application filed September 6, 1917. Serial No. 189,910.

and State of Kansas, have invented certain new and useful Improvements in Operators Circuits, of which the following is a specification.

My invention relates to operators tele phone circuits, and more particularly to such circuits for use with cord circuits and trunk circuits.

The object of my invention is the production of a highly eflicient balanced operators telephone circuit, provided With a novel test circuit in which a minimum amount of apparatus is required.

l-Icretofore it has been necessary to associate two or more repeating coils with an operators telephone circuit, where a test relay was provided, to secure the necessary test circuits and to reduce the side tone. One of the features of my invention is to provide an operators telephone circuit having the above feature and to arrange this circuit so that only one repeating coil is necessary.

Another feature of my invention is the provision of a break contact for the. test relay that removes a shunt from across a resistance adapted to be cut in series with one of the primarywindings of the repeating coil to transmit the desired busy click to the operators receiver when a busy line is tested. The provision of a break contact for the test relay produces a quicker test than'can be obtained by de-energizing the test relay instead of energizing it. I also arrange the test relay in such a manner that a revertive test tone may be transmitted to the operators receiver when the called partys substation is one connected to the calling subscribers line.

A further-feature of my invention is the connection of the operators receiver in a \Vheatstone bridge circuit to reduce the side tone.

The above features and others will be hereinafter more fully set forth in the accompanying specification and in the appended claims.

For a better understanding of my invention, reference will be made to the accompanying drawing which illustrates my invention operating in connection with a telephone exchange system which comprises a calling substation A and a called substation B connected via a cord circuit C. The substations A and B terminate respectively at the exchange in lin circuits L and L The line circuits L and L comprise the usual line relays LR and LE cut-oil relays CO and CO multiple jacks J and J and the line signals S and S respectively;

The cord circuit C for interconnecting the said substations as calling and called lines is provided with an answering plug P and a calling plug P the said plugs P and P being connected by the heavily marked conductors. The answering end of the cord circuit C is provided with an answering supcrvisory relay AS which is adapted, when the answering plug P is inserted into a jack J of a calling line, to automatically connect the operators telephone set 0 in circuit with the cord conductors, and in addition, the said relay AS controls the lighting of the answering supervisory lamp AL. Associated with the calling end of the cord circuit C. I provide a switching relay SlV, which relay is adapted to be energized, when a calling plug P is inserted into the ack of a called idle line, to disconnect the operators set 0 from the cord conductors of the said cord circuit C.

A party line ringing key RK is provided for connecting one of a plurality of generators G. G G and G to signal a subscriber at a called-for substation, and for controlling the circuit of a ringing control relay BC. The said relay RC in'turn controls the circuit of an interrupter relay IR through the agency of a constantly rotating interrupter I. and operates to intermittently connect ringing current to signal the subscriber at the called-for substation. A calling supervisory relay CS is also provided and is adapted to be energized when a response is secured from the called substation to control the calling supervisory signal CL, and also operates to interrupt the circuit of the ring ing control relay BC to disconnect the ringing current from the called substation.

The operat ons set 0, as illustrated comprises an induction coil IC built up of four windings, 1, 2, 3 and 4. and an operating relay OR- which is energized when the plug of the operators set 0 is inserted into the operators jack. The said relav OR remains in its energized position until the plug is withdrawn. The drawing does not show the plug for connecting the operatofis receiver and transmitter with the coil. IC and its associated mechanism, but this arrangement is well known and is in universal use. relay TB is also provided which is operated over a common test conductor when a busy line is testedto produce a click in the operators head receiver 6, and when an idle line is tested the relay TR does not energize but remains in its normal position. A make contact is provided for the test relay T i so that if the line tested is also the calling line and has a revertive tone connected to its test con tact, this tone will be transmitted through the primary winding 1 of the induction coil IO and repeated into the operators receiver 6. The primal Y windings 1 and 2 of the in duction coil Il are connected in multiple between the opposite poles of battery B. As before mentioned, the normal contact- 26 of relay TR closes a shunt about resistance 21 that is adapted to be connected in series with.

the primary winding 1. when the test relay TB- is energized. The connecting of the resistance 21 in series with the primary winding 1 changes the flow of current therethrough, thereby causing a click in the op erator s receiver. A resistance 30 is connected in series with the secondary windings 3 and 4: andfornis one arm of a VVheatstone bridge circuit. The windings 3 and 4t form other arms of the bridge and the circuit connecting wires extending out through contacts 8 and 9 of the relay AS form the fourth arm of said circuit. The receiver 6 is connected across thiscircuit having its one terminal connected between windings 3 and t and its other terminal connected between the resistance 30 and the resistance of said connecting conductors.

Having described in general the preferred arrangement of the circuits and a'p iaratus employed in my invention, I will now describe it more in detail operating in connection With the exchange system as illustrated. Assuming now that the subscriber at the calling substation A removes his receiver to initiatea call, the closing of the switch hook contacts at the substation A brings about the energization of the line relay LR, and the actuation ofthe said relay LR brings about the lighting of the line signal S. The operator associated with the cord circuit C, noting the lighted line signal S, inserts the answering plug P of the cordcircuit G into the answering jack J of the calling line. clos mg a series energizing circuit for the cut-off relay CO and impedance coil 7. traced from battery through the said coil 7. the sleeve contacts of the connected plug and jack, P and J, and through the winding of the cutoff relay C0 to ground. The energization of the relay CO brings about the de-ener-' gization ot'. the line relay Ll-l'. The relay Lll A test restoring effaces the signal S. The closing.

from ground through the winding of the re lay AS, tip contacts of the connected plug and jack, closed contact of the relay CO, through the substation A, back through sleeve contacts of the plug and jack, and through the winding of the impedance coil '7 to battery. The closing of alternate con tacts 8 and 9 of relay AS connects the operators set. 0 to the cord conductors through the said contacts 8 and 9, conductors 10 and 11, normalcontacts 12 and 13 of the switching relay SW and conductors 11 and 15 to the respective cord conductors. The operators plug being connected with its associated jack, a circuit is closed through relay OR over a circuit traced from battery through the winding of said relay, retardation coil 16, conductor 17, to the point 18 where the circuit divides, one path extendin through winding 20f the inductionicoil IL, conductor 19, and transmitter 20 to ground; the other path extending from the point 18, through normal contact 26 of relay TR, winding 1 of the induction coil 1C, conductor 22, conductor 19, and transmitter 20 to ground.

The operator now inquires the wants of thecalling subscriber A, and assumii 0 that it is a subscriber at the substation that is wanted, the operator then tests a multiple jack J of the wanted line by placing the tin of the calling plu P to the sleeve of a multiple jack J o the wanted line to test the line as to its idle or busy condition.

It the line being called is busy asa calling or a called line, the sleeve of the multiple jack of the line being called will be at a battery potential so that when the tip of the plug P touches the sleeye of the jack J a circuit is closed for the test relay TR associated with the operators set, 0, traced from battery on'the sleeve of the jack J to the. tip of the plug P through normal contact. 24: of the relay SW, test conductor 5, the winding of the relay TR, and alternate contact 25 of relay OR to ground. The relay TR upon energizing opens its normal contact 26; thereby removing the short-circuit or shunt from about the resistance winding 21, placing it in series with the primary winding 1 or coil IC. Between the interval that the operator touches the calling plug P to the sleeve of the multiple jack J of the called line and then removes it, the above operation takes. place.

The insertion of the resistance 21in circuit with the winding 1 ll i ; tacts 37 and 38.

notifying her of the busy condition of the wanted line. Owing to the fact that the relay TR energizes to connect the resistance 21 in series with the primary winding 1 instead of deenergizing to transmit the busy click to the operators set, this test is made very rapidly and does not depend upon the length of time that the operator holds the tip of the calling plug against the jack of the called line.

Assuming that the line tested is busy, the operator notifies the calling subscriber of the busy condition of the line, and the said calling subscriber then replaces his receiver upon the switch hook, opening the circuit of the relay AS. The operator withdraws the answering plug P from its connected answering jack J, opening the series energizing circuit of the relay CO and the impedance coil 7. All the apparatus used 111 the connection thus far is now restored to normal, and is available for use in establishing other connections.

Assuming that the operator tests the multiple jack of a called line that is idle, the placing of the tip on the plug P against the jack J does not aiicct the test relay TR, as the sleeve of the jack J is at a ground potential and no energizing circuit for relay TR is closed. The winding 21 thus remains shunted and the operator receiving no click knows that the line is idle and inserts the calling plug P into a multiple jack J of the wanted line. A circuit including switch ing relay SW and the cut-off relay CO is therefore established, causing the energizetion of these relays whereby the operation of CO extends a connection from the plug P to the substation B and removes the normal control of its line relay LR Responsive to the energization of the relay SW, its alternate contact 31 is closed to establish a circuit for the calling supervisory signal CL, traced from batterythrough the said lamp,

' normal contact 32 of relay CS and alternate contact 31 of relay SW to ground. The opening of the normal contacts 12 and 13 of relay SW disconnects the operators set 0 from the cord conductors, and the interruption of normal contact 24 of relay SIV disconnects the test conductor 5. The operator now depresses the proper ringing key plunger, 33, 34, 35 or 36, to its fully de pressed position, closing the end spring con The closing of alternate contact 38 establishes an energizing circuit for the ringing control relay R(J,traced from battery through the winding of relay RC, alternate contact 38, conductor 39, normal contact 32 of relay CS, to ground at alternate contact 31 of relay SW. Upon the energization of the relay RC, its alternat contact 40 is closed, establishing a locking circuit for itself traced from battery through the winding of the said relay RC, said alternate contact 40, normal contact 32 of relay CS, to ground at alternate contact 31. The closing of alternate contact 42 of relay RC establishes an intermittent energizing circuit for the interrupter relay IR, traced. from battery through the winding of the relay IR, normal contact 37 of the end springs, alternate contact 42 of relay RC, and through the constantly rotating interrupter I to ground. The relay IR is therefore alternately energized and de-energized, alternately connecting the ringing current and the supervisory relay CS in bridge of the called line.

Upon a response being secured from the called subscriber, upon the following deenergization of interrupter relay IR, a circuit for the calling supervisory relay CS is established, traced from ground through the winding of CS, normal'oontact 43 of relay IR, alternate contact 24 of relay SW, over the called line, returning through the winding of the switching relay SIV to battery. Relay CS thereupon energizes, interrupting its normal contact 32, whereby the supervisory signal CL is efiaced, and the holding circuit of the ringing control relay RC is interrupted. The relay RC thereupon restores, interrupting the operating circuit of the interrupter relay IR, at contact 42.

If the called line tested had been the calling line and a cord circuit had been used for establishing the connection that connects a tone test to the answering jack of the line, then when the tip of the calling plug was brought into engagement with a multiple jack of the line, the relay TR would have been energized as before mentioned, and the tone test would have been connected through alternate contact 26 of relay TR and through the primary winding of the induction coil IC to ground, causing the tone to be induced in the secondary windings of the induction coil to the operators receiver.

After the subscribers have finished con versation, they will replace their receivers upon their respective switch hooks, whereby the circuits of the answering supervisory relay AS and the calling supervisory relay (1S are interrupted, causing the restoration of the said relays and lighting the answering supervisory lamp AL and the calling supervisory lamp CL. The operator noting the lighted signals, withdraws the plugs P and P from the connected jacks J and J and thereby brings about the restoration of the apparatus employed in establishing the con nection.

In an operators set in which a test relay is employed, a secondary induction coilis most commonly used to reduce side tone, but with the arrangement as shown and described I do away with this second coil and use the balancing winding 30 to form one of the legs of the bridge in combination with Ill! It is to be understood that I donot wish to be limited to the exact matter shown, as various other arrangements may readily suggest themselves to one skilled in the art. Therefore, I desire to cover all such changes and modifications as come within the spirit and scope of the appended claims.

What I claim as new and desire to secure by United States Letters Patent is:

1. An 0 erators telephone circuit including an in uction coil provided with a pair of primary windings, a test relay, a resist ance normally short-circuited but adapted to be placed in circuit with one of saidprimary windings only, and means for energizingsaidtest relay to place said resistance in serieswith said winding to cause a change in the current flow through said winding wherebya signalis transmitted to theoperators receiver. r

2. An operatorstelephone circuit includingan induction coil provided with a primary winding, a resistance coil adapted to be connected in circuit'wit-h' said primary winding, a test relay provided with contacts normally shunting said resistance coil, and means for energizing-said test relay whereby the shunt from around said resistance coil will be opened and the current flow of said primary winding reduced to indicate to the operator that a busy linehas been tested.

3; An operators telephone circuit includ ing an induction coil provided with a primary winding and a secondary winding, a resistance coil in series circuit with said primary winding, a test relay provided with contacts normally closin a shunt around said resistance coil, said test relay being adapted to be operated when a busy called line is tested to remove the shunt from around said resistance coil to change the flow of current through said rimary; winding thereby inducing an impulse of current in said secondary-windin to indicate to the operator that thecalled ine tested is busy.

4. An operators telephone circuit including an induction coil provided with a pair of primary windings connectedyin multiple, a resistance coil, a test relay, contacts controlled by said test relay for connecting said resistance coil in circuit with one of the said primary windings to change the current flow therethrough, and an operators receiver affectedby the change of current flow through said primary winding.

5. An operators telephone circuit includ ing anvinduction coil provided with a pair of primary windings and a pair of secondary windings, said primary windings being normally connected in multiple with the opposite poles of a battery, a subscribers tele- 6. A telephone system including anoperv ators telephone circuit provided with an in duction coil having primary and secondary windings, a subscribcrs telephone line provided with a jack at the central exchange, an operatofis cord circuit, means for connecting said operators telephone circuit to said cord circuit, a test relay for said operators telephone circuit adapted to be energized when the calling plug of said cord circuit is ap plied to said jack if said subscribers telephone line is busy, a normally short circuited resistance in circuit withthe )rimary winding of said induction coil, ant contacts controlled by said test ielayi'or removing the shunt circuit from around said resistance, whereby the current flow through said primary winding is changed to transmit tothe operator the busy condition of said subscribersline.

7. A telephone system including subscribers telephone lines, a cord circuit for interconnecting said'lines, an operators telephone circuit p'rovided"with an induction coil automatic means for connecting said operators telephone circuit to said cord circuit. a testrelay for said operators circuit adapted to be energized when the calling plug of said cord circuit is applied to the jack of a busy oneof said subscribers telephone lines, a normally shunted resistance included in series circuit with a primary winding of said induction coil, and means controlled by said test relay for removing the shunt from about said resistance to change the current flow. in said primary winding, thereby notifying the operator that the tested called line is busy.

ScAn operators telephone circuit including an induction coil provided with a primary winding, a test conductor, a test relay connected in circuit withsaid test conductor, and contacts-controlled by said test relay for connecting said test conductor in circuit with said primary winding of said induction coil. 7

9. An operators telephone circuit including an induction coil, a test conductor, a test relay connected in circuit with said test conductor, a resistance coil, and contacts controlled by said test relay for connecting said resistance in series with a primary winding of said induction coil and for connecting said test conductor in circuit with said primary winding.

10. An operators telephone circuit including an induction coil provided with a pair of primary windings normally connected in parallel, a test relay, a resistance adapted to he placed in circuit with one of said primary windings, and means for energizing said test relay to place said resistance in series with said primary winding, thereby causing a change in the current flow through said primary winding.

11. An operators telephone circuit including an indication coil provided with a primary winding, a test relay individual to the operators telephone circuit, a pair of normally closed contacts for said test relay, and means for operating said test relay to open said normally closed contacts, thereby changing the current flow through said primary winding to transmit a signal to the operator.

122. An opcratofis telephone circuit including a receiver and an induction coil provided with a primary winding, a test relay, :1 pair of normally closed contacts for said test relay controlling a circuit through said primary winding, and means for energizing said test relay when a busy called line is tested to cause said relay to open its normally closed contacts to transmit an audible signal to the operators receiver.

13. An operators telephone circuit includ ing an induction coil provided with a pair of primary windings, a resistance coil no-1 mally in circuit with said primary windings, a second resistance coil, and means for connecting said second resistance coil in circuit with one of said primary windings to cause a change in current flow through said primary winding to transmit a signal. to the operator.

14-. An operators telephone circuit including an induction coil provided with a primary winding, a resistance coil normally in circuit with said primary winding, a second resistance coil, and a test relay for connectingsaid second resistance coil in circuit with said primary winding to cause a change in the current flow through said primary winding.

15. An operators telephone circuit includ ing an induction coil provided with a pair of primary windlngs, a reslstance coll connected in circuit with said primary windings, a test relay, and means for energizing said test relay to connect a second resistance in circuit with one only of said primary windings.

16. An operators telephone circuit including an induction coil provided with a pair of primary windings connected in multiple, a resistance connected. in circuitwith said primary windings, a second resistance, and means for connecting said second resistance in circuit with one only of said primary windings.

17. An operators telephone circuit includ ing an induction coil having a primary winding, a normally shunted resistance connected in circuit with said primary winding, a test relay connected to a test conductor, and means for energizing said test relay to remove said shunt from about said resistance and to connect said primary winding to said lest conductor.

18. An operators telephone circuit including an induction coil provided with a pair of primary windings connected in multiple, a test relay connected to a test conductor, and means for ener 'izing said test rclay to connect one of saic primary windings to said test conductor,

19. An operators telephone circuit i11- cluding an induction coil having a pair of primary windings and a air of secondary windings, a resistance coil adapted to be connected in circuit with a primary winding of said induction coil but normally shunted therefrom, a test relay, and means for ener-' gizing said test relay when a busy line is tested to remove said shunt from about said resistance thereby placing said resistance in series with said primary winding.

20. An opcrators telephone circuit including an induction coil having a pair of primary windings and a pair of secondary windings, a resistance coil adapted to be connected in circuit with a primary winding of said induction coil but normally shunted therefrom, a test relay, and means for energizing said test relay when a busy line is tested to remove said shunt from about said resistance thereby placing said resistance in series with said primary winding, thus changing the current flow through said primary winding and inducing an impulse of current in said secondary windings to transmit a signal to the operator.

Signed by me at Kansas City, in the county of Jackson and State of Missouri, this 21 day of August, 1917.

HAROLD T. WHITE. 

